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M. C. Neville, V. S. Sawicki, and W. W. Hay Jr


In order to determine whether short term variations in plasma glucose and/or insulin influence milk lactose secretion in women, the effects of fasting and increased blood insulin and glucose on milk volume and composition were studied with glucose clamp methodology in exclusively and partially breast-feeding women. Twenty hours of fasting had no discernable effect on the output of milk or its macronutrient composition. Four hours of increased plasma insulin, studied under conditions where plasma glucose was maintained at the fasting level, had no effect on milk volume, milk glucose concentration, total fat content or lactose secretion rate. Increased plasma glucose, maintained at twice fasting levels for 4 to 6 h, produced a threefold increase in milk glucose concentration but had no significant effect on the rate of lactose synthesis. In partially breast-feeding women producing no more than 200 ml milk per day, a similar degree of hyperglycaemia increased milk glucose more than fourfold but did not significantly increase the milk secretion rate. It is concluded that human milk production is isolated from the homeostatic mechanisms that regulate glucose metabolism in the rest of the body, in part because the lactose synthetase system has a K m for glucose lower than the concentration available in the Golgi compartment.

Journal of Endocrinology (1993) 139, 165–173

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J. B. Hay, D. Meddis, A. J. Thody, and S. Shuster

The metabolism of testosterone and 5α-dihydrotestosterone has been studied in vitro in preputial glands of posterior hypophysectomized, totally hypophysectomized and control sham-operated rats. The level of C19 steroid 5α-reductase activity/unit of preputial gland DNA did not fall after removal of the neurointermediate lobe and rose after total hypophysectomy. It was concluded from this that the androgen unresponsiveness of the preputial glands of hypophysectomized rats was not due to a near-total lack of 5α-reductase and hence that the combined synergistic action of testosterone and α-melanocyte-stimulating hormone (α-MSH) on preputial gland activity was unlikely to be due to an α-MSH-mediated restoration of 5α-reductase levels in hypophysectomized rats. Levels of 3α-and 3β-hydroxysteroid dehydrogenase but not of 17β-hydroxysteroid dehydrogenase appeared to be altered by hypophysectomy.

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DM Findlay, LJ Raggatt, S Bouralexis, S Hay, GJ Atkins, and A Evdokiou

We recently reported that calcitonin (CT) can profoundly inhibit the growth of HEK-293 cells transfected with the human calcitonin receptor (hCTR). We also obtained preliminary evidence that suggested a role for CT in cell survival, and in the present study we have investigated the pro-apoptotic action of CT, which we observe in conditions of low serum concentration. Under these conditions, we have found that CT treatment of HEK-293 cells stably transfected with the insert-negative form of the human CTR (HR12 cells) caused a time-dependent decrease in cell number associated with loss of cellular attachment. Loss of cellular adherence in CT-treated cultures caused programmed cell death, as shown by Annexin V staining of cells, failure of cells to exclude Trypan Blue dye, condensation and cleavage of nuclear DNA, and appearance of hypodiploid cells in fluorescence-activated cell sorting (FACS) analysis. The accumulation of non-adherent cells and cell death was concomitant with increased intracellular activity of caspase-3. However, inhibition of caspase activation in HR12 cells did not prevent CT-mediated loss of attachment and did not maintain the viability of non-adherent cells, indicating that caspase activation accompanied, but was probably not the cause of, the loss of cell viability. Neither the effects of CT on cell survival nor the activation of caspase-3 were observed in serum-replete conditions, suggesting that serum-derived factors provide protection of cells from CT-induced apoptosis. The inhibitory effects of CT on cell growth were found previously to be related to activation of Erk1/2 MAP kinase. In the present experiments, it was found that the Erk1/2 inhibitor, PD 98059, inhibited the CT-induced loss of cellular adherence and the consequent reduction in cell numbers. These results demonstrate that CT can negatively affect cell survival and they identify roles for cell adherence and MAP kinase activation in this process.